…n wrench. r=nical

* Add a script for running wrench under various software rasterizers.
* Add support to wrench for non-blocking event loop.
* Add support to wrench for selecting GL/ES rendering API.
* Update x11 bindings for wrench, to fix a release only crash.

Differential Revision: https://phabricator.services.mozilla.com/D36551

[wrupdater] From https://hg.mozilla.org/mozilla-central/rev/d066f9f4b7bcf5d3b692ca5a198406e1ff358076